Fuel injection valve for internal combustion engines

ABSTRACT

A fuel injection valve for internal combustion engines, having an axially displaceable valve member which is disposed in a valve body. On an end toward an engine combustion chamber the valve member has a conical valve sealing face with which the valve member cooperates with a conical valve seat face on the valve body for controlling an injection cross section. Via an internal guide the valve member is guided slidingly displaceably on a tang of a stationary insert body.

PRIOR ART

The invention is based on a fuel injection valve for internal combustionengines. In one such fuel injection valve, known from U.S. Pat. No.4,972,997, a pistonlike valve member is guided axially displaceably in abore of a valve body. The valve member, on its end toward the combustionchamber, has a conical valve sealing face, with which it cooperates witha conical valve seat face on the valve body, which face is formed on theinward-projecting end of the closed valve bore. A contact edge betweenthe valve sealing face on the valve member and the valve seat face formsan encompassing sealing edge. This sealing edge, formed when theinjection valve is closed, thus seals off a pressure chamber, adjoiningthe sealing edge upstream of the pressure chamber, when the injectionvalve is closed. Downstream of this sealing edge, at least one injectionopening that discharges into the combustion chamber of the engine to besupplied is provided in the wall of the valve body and leads away fromthe valve seat face.

However, this known fuel injection valve has the disadvantage that thecontrol times of the valve member, because of the strong hydraulicforces on the valve member, are too long for injection valves thatswitch at very high speed. The known fuel injection valve is thereforevery large, because there are so many components axially in line withone another, which limits the utility of the known fuel injection valvesin engines where the available installation space is scarce.

ADVANTAGES OF THE INVENTION

The fuel injection valve of the invention for internal combustionengines, has an advantage over the prior art that very slight controlforces and thus very rapid valve stroke motions of the valve member ofthe injection valve are possible. These rapid adjustment motions becomepossible because of the small hydraulically operative surface areas ofthe valve member and the small control volume, since only small movingmasses have to be displaced. This is advantageously attained in that thevalve member has a guide bore, with which it is slidably displaceablyguided on a tang of a stationary insert body. The displaceable valvemember is hydraulically pressure-balanced in the intervals betweeninjections, so that no leakage losses occur. Thus sealing from theoutside for outflowing leaking oil is unnecessary, and along with theleakage heat development and any possible entry of dirt can also bereduced, because of the good separation between sealing components andguidance components. A further advantage is attained because of the veryshort structural design of the fuel injection valve of the invention; asa result, the required installation space in the engine to be suppliedcan also be reduced sharply. The restoring spring that urges the valvemember of the injection valve in the closing direction merely needs toclose the injection valve when the system is pressureless, and thus itcan be made correspondingly small in size. During thehigh-pressure-filled mode, the closing movement and the holding of thevalve member on the valve seat face are effected by means of the designof the hydraulic opening and closing faces that are operative at thevalve member. The hydraulic engagement area of the closing faces on thevalve member, when the injection valve is closed, is greater than thehydraulic engagement areas acting in the opening direction. The openingstroke motion of the valve member is advantageously limited bymechanical stroke stop faces on the tang of the stationary insert body,but hydraulic stroke stops are alternatively possible as well. Thecontrol valve that opens the control chamber into a relief chamber canbe embodied as a 2/2-way magnet valve, as shown in the exemplaryembodiment, but 2/3-, 3/2- or 3/3-way control valves can also be used asan alternative. The valve member is guided axially over its inner guidebore on the tang of the stationary insert body, but it is also possibleto provide a further guide on the outer circumference of the valvemember, inside the valve body, in addition. When this kind of improvedguide is used, fuel flow openings on the valve member are provided whichenable a flow of fuel from a pressure chamber to the valve seat faces;these openings can be embodied as ground face sections on the jacketface of the valve member, or as through bores. The valve member itselfcan advantageously be embodied in two parts, with a headpiece that hasthe valve sealing face being inserted, preferably press-fitted, into asleeve. This kind of two-piece valve member can be produced in a simpleway and with high precision. A further advantage of the fuel injectionvalve of the invention is the possibility of hydraulically floatingsupport of the insert body, carrying the tang, in the valve body, sothat the insert body, and the valve member guided on the insert body,can be reliably centered relative to the valve body.

Further advantages and advantageous features of the subject of theinvention can be learned from the description, drawing and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Five exemplary embodiments of the fuel injection valve of the inventionfor internal combustion engines are shown in the drawing and describedin detail in the ensuing description.

FIG. 1 shows a first exemplary embodiment of the fuel injection valve ina longitudinal section, in which the fuel delivery and relief of thecontrol chamber or work chamber between the tang and the valve member iseffected via a central through bore in the tang;

FIG. 2 shows an enlarged detail of the valve member of FIG. 1, which isin two parts and is guided on the tang;

FIG. 3 shows a second exemplary embodiment of the fuel injection valve,in which the valve member has an additional external guide in the valvebody;

FIG. 4 shows a third exemplary embodiment with a stroke stop for thevalve member formed by a shoulder on the circumference of the tang;

FIG. 5 shows a fourth exemplary embodiment of the fuel injection valve,in which the stroke stop of the valve member is formed by a stepped endface of the tang; and

FIG. 6 shows a fifth exemplary embodiment of the fuel injection valve,in which the work or control chamber is disposed outside the tang of theinsert body.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The exemplary embodiment, shown in FIG. 1, of the fuel injection valveof the invention for internal combustion engines has a cylindrical valvebody 1, which protrudes with its free lower end into a combustionchamber, not identified by reference numeral, of the engine to besupplied. The valve body 1, embodied as a hollow body, is braced axiallyby a lock nut 3 against a valve holding body 5; an insert body 7 isfastened between the end faces, facing one another, of the valve body 1and of the valve holding body 5. This stepped, cylindrical insert body7, on its end remote from the valve holding body, has a tang 9 withwhich it protrudes into the interior of the valve body 1. On the freeend of the tang 9, a cylindrical valve member 11 is axially displaceablyguided with a central guide bore 13. This valve member 11, on its closedface end remote from the tang 9, has a conical valve sealing face 15,which is divided into two regions with different cone angles; at thetransition between the two cone angles of the valve sealing face 15, anencompassing sealing edge 17 is formed on the valve member 11. With itsvalve sealing face 15, the valve member 11 cooperates with a valve seatface 19 formed on the closed, inward-projecting end of the interior inthe valve body 1; when the valve member 11 is on the valve seat face 19,the sealing edge 17 on the valve member 11 divides an upstream pressurechamber 21, formed in the interior of the valve body 1, from a blindbore 23 located downstream of the sealing edge 17, from whose valve seatface 19 downstream of the sealing edge 17 injection openings 25 leadaway into the engine combustion chamber. For secure contact of the valvemember 11 with the valve seat face 19 when the system is pressureless, arestoring spring 27 is fastened between an annular end face 29, remotefrom the valve seat 19, on the valve member 11 and a shoulder 31 on thetang 9, and the restoring spring urges the valve member 11 in thedirection of the valve seat face 19. A hydraulic work or control chamber37 is also formed, between the end face 33 on the closed end of theguide bore 13 in the valve member 11 and the end face 35 of the tang 9.This control chamber 37 is filled with fuel at high pressure andrelieved via an axial through bore 39 in the insert body 7. To that end,the through bore 39 is connected, via a throttle bore 41 in the valveholding body 5, to a high-pressure line 43, which in turn discharges ata high-pressure storage chamber, not shown in further detail, which isconstantly filled with fuel at high pressure via a high-pressure feedpump and to which preferably all the injection valves of the injectionsystem are connected. For pressure relief of the control chamber 37, thethrough bore 39 discharging into it communicates with a relief line 45in the valve holding body 5; this line discharges into a low-pressurerelief chamber, not shown in further detail, and is closable by means ofa control valve 47. This control valve 47, which can be triggeredarbitrarily from outside, is embodied in this exemplary embodiment as a2/2-way valve and is preferably actuated by a magnet valve.

For adjusting the valve member 11, the annular end face 29 and the endface 33 of the guide bore 13 act as hydraulic pressure engagement faceson the valve member 11 that act in the closing direction. In the openingdirection, the valve sealing face 15 is active; when the valve member 11is on the valve seat 19, initially its region adjoining the sealing edge17 upstream is active. The valve diameter at the sealing edge 17 forms afirst diameter d1; the diameter of the outer circumference of thecylindrical valve member 11 forms a second diameter d2; and the diameterof the outer circumference of the tang 9 forms a third diameter d3. Thediameter d3, for reliable function of the fuel injection valve, must begreater than the diameter d1, which defines the seat diameter at thevalve sealing seat.

The fuel injection valve of the invention functions as follows: At theonset of operation of the injection system, the high-pressure storagechamber, not shown in detail, is filled with fuel at high pressure bythe high-pressure fuel pump. This pressure is carried via the individualhigh-pressure lines 43 to the various injection valves protruding intothe engine combustion chamber. In the process, the high fuel pressure,in the first exemplary embodiment, reaches the pressure chamber 21 viathe high-pressure line 43 and the control chamber 37 via the throttlebore 41 that branches off from the high-pressure line 43 and via thethrough bore 39 in the insert body 7. The control valve 47 keeps therelief line 45 closed under these circumstances. In this closed state ofthe fuel injection valve during the intervals between injection, theannular end face 29 and the end face 33 of the inner guide bore 13 onthe valve member 11 act in the closing direction and thus urge the valvemember 11 toward the valve seat face 19. At the same time, the high fuelpressure in the pressure chamber 21 engages the valve member 11 in theopening direction, at the valve seat face 19 formed upstream of thesealing edge 17. The hydraulic pressure engagement faces on the valvemember 11 are embodied in such a way, however, that in this situationthe faces 29, 33 acting in the closing direction are larger than theareas of the valve sealing face 15 acting in the opening direction, andthus the valve member 11 is held hydraulically in contact with the valveseat face 19. If an injection at the injection valve is to take place,then the control valve 47 is actuated in the opening direction, causingthe control valve to open the relief line 45 into a low-pressurechamber. As a consequence, the pressure in the control chamber 37 dropsvery quickly via the through bore 39 into the relief line 45, so thatthis hydraulic pressure force engaging the valve member 11 in theclosing direction is reduced. Since the pressure engagement area on thevalve sealing face 15 that acts in the opening direction is greater thanthe annular end face 29 acting in the closing direction, the valvemember 11 is lifted from the valve seat 19 counter to the force of therestoring spring 27, so that the fuel can flow out of the pressurechamber 21 via the opening cross section uncovered between the valveseat face 19 and the valve sealing face 15, into the injection openings25 and on into the engine combustion chamber. The throttle bore 41assures that the high fuel pressure flowing in from the high-pressureline 43 will not immediately flow out in a short circuit into the reliefline 45. The injection at the injection valve is ended when the controlvalve 47 re-closes the relief line 45, so that in the control chamber37, via the bores 41 and 39, a high fuel pressure can build up againthat then, via the engagement face 33 and the annular end face 29, againdisplaces the valve member 11 into contact with the valve seat face 39.Since when the injection valve is closed the hydraulic pressure insideand outside the displaceable valve member 11 is of equal magnitude, anyleakage flow at the valve member 11 into the low-pressure chamber can beaverted. The valve member 11, during its reciprocating motion, is thussecurely guided axially slidingly displaceably by means of its internalguidance on the tang 9 of the insert body 7.

In FIG. 2, one possible embodiment of the valve member 11 as a two-piececomponent is shown in an enlarged, fragmentary detail view. The valvemember 11 has a sleeve 49, which is guided slidably displaceably by itsinside diameter on the tang 9 of the insert body 7, and into whose lowerend, toward the combustion chamber, a headpiece 51 embodied as a steppedcylinder is press-fitted, which headpiece has the valve sealing face 15and the sealing edge 17 on its face end remote from the sleeve 49. Theheadpiece 51 is preferably inserted with a tanglike extension into theinner diameter of the sleeve 49 and welded at the annular shoulder faceto the annular end face of the sleeve 11.

In FIG. 3, a second exemplary embodiment of the fuel injection valve ofthe invention is shown, in which the valve member 11, in addition to theinternal guidance on the bore 13, is guided via an external guide on theinner wall of the valve body 1. The outer circumferential wall 53 of thevalve member 11 forms this second, additional guide face that slides onthe inner wall face 55 of the valve body 1. For fuel passage from thepressure chamber 21 to the valve seat face 19, recesses are provided onthe outer circumference of the valve member 11, which are preferablyembodied as ground face sections 57.

FIGS. 4 and 5 show two further exemplary embodiments of the fuelinjection valve, in which to limit the opening stroke motion of thevalve member 11, various mechanical stroke stops are provided. FIG. 4shows a third exemplary embodiment, in which the stroke stop for thevalve member 11 is embodied as an annular shoulder 59 on the jacket faceof the tang 9 of the insert body 7. With this annular shoulder face 59,the valve member 11 comes into contact, after completing its totalopening stroke course, with the annular end face 29.

Filling of the control chamber 37 between the tang 9 and the closed endface 33 of the guide bore 13 in the valve member 11 also now takes placedirectly from the pressure chamber 21, to which end a throttle bore 61is provided in the valve member 11; beginning at the control chamber 37,this bore discharges into the pressure chamber 21 at the jacket face ofthe valve member 11.

The fourth exemplary embodiment shown in FIG. 5 differs from the thirdexemplary embodiment shown in FIG. 4 only in the type of stroke stop forlimiting the opening stroke motion of the valve member 11. The openingstroke of the valve member 11 is now limited by the contact of the endface 33 of the bore 13 in the valve member 11 with the end face 35 ofthe tang 9 of the insert body 7. To that end, the annular end face 35 ofthe tang 9 has a shoulder 63, which is axially offset inward and whichassures that the end face 33 on the valve member 11 acting in theclosing direction will be preserved. In this way, by means of thecontrol valve 47 in the event of wear of the relief line 45, at the endof the injection phase and with refilling of the control chamber 37 withfuel at high pressure via the throttle bore 61, the restoring motion ofthe valve member 11 to the valve seat 19 can remain reliably assured.The opening stroke course of the valve member 11 can be adjusted in asimple way via the axial length of the stationary insert body 7.

In the fifth exemplary embodiment shown in FIG. 6, the control chamber37, unlike the preceding exemplary embodiments, is disposed outside thevalve member 11. To that end, analogously to the second exemplaryembodiment, the valve member 11 is guided both inside on the guide bore13 and outside on the circumferential wall 53 of the valve member 11. Achamber formed between the rear annular end face 29 on the valve member11 and the shoulder 31 on the stationary insert body 7 forms the controlchamber 137 in the fifth exemplary embodiment, and the restoring spring27 is also disposed in it. A relief conduit 64 leads away from thecontrol chamber 137 and can be opened by the control valve 47 into therelief line 45. The hydraulic work chamber 65 enclosed between the endface 35 of the tang 9 and the closed end face 33 of the bore 13 on thevalve member 11 is refilled with fuel at high pressure from ahigh-pressure fuel collection tank via a through bore 39 and ahigh-pressure line 43. A connecting bore 67 leads away from thehydraulic work chamber 65 and discharges into a chamber, near the valveseat, inside the valve body 1. The high-pressure fuel supply to thecontrol chamber 137 is effected via a throttle bore, which from thethrough bore 39 in the insert body 7 discharges into the control chamber137.

In the fifth exemplary embodiment, the opening stroke motion of thevalve member 11 is effected by the pressure relief of the externallylocated control chamber 137 via the relief conduit 64 and the reliefline 45. The end face 33 inside the valve member 11, with its diameterd3, continues to act in the closing direction of the valve member 11.The hydraulic pressure area, that engages the valve member 11 in theopening direction and formed by the difference in diameter between theouter circumference of the valve member 11 (d2) and the diameter at theseat edge 17 (d1), must be greater than the end face 33 on the valvemember 11 now acting solely in the closing direction. The closing strokemotion of the valve member 11 is effected, analogously to the precedingexemplary embodiments, by the renewed closure of the relief line 45, asa consequence of which a high fuel pressure builds up again in thecontrol chamber 137 via the throttle bore 41; this pressure urges thevalve member 11, at the annular end face 29 in addition to the end face33, in the closing direction and thus pushes the valve member 11 backinto contact with the valve seat face 19.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed is:
 1. A fuel injection valve for internal combustionengines, comprising an axially displaceable valve member (11), saidvalve member is disposed in a valve body (1) and on an end toward anengine combustion chamber has a conical valve sealing face (15), saidconical sealing face cooperates with a conical valve seat face (19) onthe valve body (1), the conical valve sealing face (15) on the valvemember (11) has an annular edge that forms a sealing edge (17), andincludes at least one injection opening (25) into the engine combustionchamber, in a region of the valve seat face (19) adjoining the sealingedge (17) of the valve member when the injection valve is closed, thevalve member (11) has a guide bore (13), with which the valve member isslidably displaceably guided on a tang (9) of a stationary insert body(7).
 2. The fuel injection valve according to claim 1, in which in thevalve body (1), a high-pressure chamber (21) is formed, which dischargesat the valve seat face (19) and which communicates constantly, via ahigh-pressure line (43), with a high-pressure storage chamber filledwith fuel at high pressure.
 3. The fuel injection valve according toclaim 1, in which between a closed end face (33) of the guide bore (13)in the valve member (11) and an end face (35) of the tang (9) of theinsert body (7), a work chamber is defined which is filled with fuel athigh pressure from the high-pressure chamber (21) or the high-pressureline (43).
 4. The fuel injection valve according to claim 1, in which acontrol chamber (37, 137) which is filled with high fuel pressure isprovided in the valve body (1), and an internal pressure urges the valvemember (11) in a closing direction, and the control chamber ispressure-relieved into a low-pressure chamber via an openable reliefline (45).
 5. The fuel injection valve according to claim 4, in which acontrol valve (47) actuatable from outside is inserted into the reliefline (45).
 6. The fuel injection valve according to claim 3, in whichthe control chamber (37) is formed by the work chamber between the endface (33) on the valve member (11) and the end face (35) on the tang(9).
 7. The fuel injection valve according to claim 4, in which thecontrol chamber (37) is formed by the work chamber between the end face(33) on the valve member (11) and the end face (35) on the tang (9). 8.The fuel injection valve according to claim 6, in which the controlchamber (37) communicates with the high-pressure line (43) or thehigh-pressure chamber (21) via an inlet conduit that includes a throttlerestriction (41).
 9. The fuel injection valve according to claim 7, inwhich the control chamber (37) communicates with the high-pressure line(43) or the high-pressure chamber (21) via an inlet conduit thatincludes a throttle restriction (41).
 10. The fuel injection valveaccording to claim 4, in which the control chamber (137) is disposedradially outward of the tang (9) of the stationary insert body (7) andis defined by an annular end face (29), remote from the combustionchamber, of the valve member (11).
 11. The fuel injection valveaccording to claim 10, in which the control chamber (137) is made tocommunicate constantly with the high-pressure line (43) via a throttlebore (41) and is made to communicate with a low-pressure chamber via aconnectable relief line (45).
 12. The fuel injection valve according toclaim 1, in which a restoring spring (27) that urges the valve member(11) in the closing direction is fastened between the valve member (11)and the insert body (7).
 13. The fuel injection valve according to claim1, in which the valve member (11) is formed by a sleeve (49), having anopening toward the combustion chamber, a head piece (51) is insertedinto the opening, and the valve sealing face (15) is disposed on a faceend of the head piece remote from the sleeve (49).
 14. The fuelinjection valve according to claim 1, in which the opening stroke lengthof the valve member (11) is limited by a stroke stop.
 15. The fuelinjection valve according to claim 14, in which the stroke stop isformed by an annular shoulder (59) on the cylindrical tang (9) of theinsert body (7).
 16. The fuel injection valve according to claim 14, inwhich the stroke stop is formed by a shoulder (63) on the side towardthe valve member of the annular end face (35) of the tang (9) of theinsert body (7).
 17. The fuel injection valve according to claim 1, inwhich the valve member (11) is additionally guided by a radial jacketface (53) on an inner wall (55) of the valve body (1), and throughconduits (57, 67) provided on the valve member (11) for fuel flow.